Things about the human body that still can't be explained

The human body is truly a magnificent chunk of nature. It's capable of throwing 100-mile-per-hour fastballs, delicately gliding across a sheet of ice while pulling off insane triple-axels, and landing on the freaking Moon! Yes, the human body is, in many ways, a work of natural perfection—and scientists have been hard at work uncovering its mysteries. Yet when it comes to some really basic parts of it, we're all but stumped.

Yawning

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We do it when we're tired. We do it when we're bored. We do it when we see other people do it. Indeed, we all know when we yawn—but science still hasn't figured out the definitive reason for it.

Yawning was previously believed to be the body's involuntary attempt at getting more oxygen into the blood, but this theory has been all but discarded. Instead, University at Albany psychology professor Gordon Gallup believes yawning is the body's way of dealing with a hot head by literally cooling off the brain. Gallup claims the things we associate with causing yawns—such as not getting enough sleep at night—cause the brain to run hot, requiring our body to turn up the AC. When we yawn, the hotter blood in the brain is theoretically replaced with the heart's cooler blood, in a process that causes the cooler ambient air to trade with our body's warmer, body-temperature air. Sounds fair enough, but this idea has yet to be proven, and not everyone is buying it.

Scientists are pretty sure, however, that yawning is one of our most primitive, unconscious bodily functions—and is one of the very first things we ever do! Fetuses yawn during the first trimester in the womb, according to The New Yorker. Yawning also links us to the rest of the animal kingdom, as Charles Darwin suggested in 1838, when he wrote that "seeing a dog & horse & man yawn makes me feel how much all animals are built on one structure."

Contagious yawning may stem from a variety of things. Some scientists believe it's a sign of empathy. Perhaps the best theory is that yawning when others yawn is a carryover from our primitive ancestors' society, when verbal communication was more limited, and yawning was an important social signal that it's time to act. In fact, there's an extremely high chance you yawned while reading this, or when looking at the above picture.

So next time you yawn, remember that you're getting in touch with your primitive ancestors. And if you're prone to long, extended yawns, rejoice! Big yawns correlate with big brains. You're not rude: you're a genius.

The appendix

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If you're reading this, there's about a 1 in 15 chance you've had your appendix removed—or will at some stage of your life. Scientists and doctors aren't totally what the small, 3.5-inch tube inside our bodies does, and it's well documented that we can live without it. So, why do we even have it?

The traditional explanation was that the appendix was vestigial, used by our evolutionary ancestors and then just left over in the body. But some scientists, like Loren G. Martin, professor of physiology at Oklahoma State University, reckon that the appendix does serve some function today. According to Martin, the appendix serves an important role in the development of the fetus, as well as in young adults, producing all kinds of compounds that keep the body running well. We feel like just taking Martin's word on that, given we're not really in any position to argue, but the professor does mention that the detailed role of the appendix and associated function are "currently under investigation."

The appendix appears to be most useful as a backup, if and when someone has their urinary bladder removed. Notes Martin, doctors can grab your appendix and fashion it into a replacement urinary sphincter. But we're pretty sure nature didn't exactly intend that use for it.

Big breasts

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Pubescent boys go crazy for them. Adult men go crazy for them. Women are supposed to keep them covered up, despite many states making it legal for a woman to be topless anywhere a man is legally allowed to be. Yes, breasts are definitely a thing—but have you ever noticed that humans are the only ones with, generally speaking, permanently enlarged breasts?

Why humans have enlarged breasts, when other primates don't, is still a mystery. In non-human primates, enlarged breasts are a clear indicator that a mother is suckling young, while full breasts on a human are not even a positive indicator of fertility. It could just be a matter of sex appeal. Male ancestors liked plump, symmetrical breasts, so evolution selected for them.

Not everyone buys this reasoning, though, as some believe the human breast is the result of evolution pertaining to lactation. Florence Williams, author of Breasts: A Natural and Unnatural History, believes that big boobs are probably a result of natural selection pertaining to both male sexual preference and ease of lactation, telling Salon, "There's no doubt at all that a lot of men are really, really attracted to breasts! But it could be that that attraction came later or was secondary, and it's never really been satisfactorily proven that all men in all cultures across all times are obsessed with breasts."

Whether they're big because of survival, sexual preference, or both, the human female breasts remain to all of us—like a 12-year-old rummaging through the attic for his uncle's Playboy stash—a confounding mystery.

Blushing

Charles Darwin called blushing, as noted by The Atlantic, "the most peculiar and most human of all expressions" in The Expression of the Emotions in Man and Animals. The science behind blushing itself isn't a mystery—the capillaries in the face near the surface of our skin expand, letting the blood rush right on in, creating a flushed appearance. Aside from that very basic fact, blushing remains a quite a conundrum in the study of human physiology and psychology. We know what blushing is … we just don't know why we blush.

One theory is that blushing is somewhat of a built-in lie detector, signaling sincerity, likeability, and trustworthiness. Another suggests blushing is a way for your body to cool your brain, when an excess of warm blood floods your brain in situations we find embarrassing. Various other theories suggest blushing is an involuntary, nonverbal form of communication, signaling something is wrong with a situation. It could also signal an involuntary apology. One thing seemingly all theories agree with is that blushing is seen socially as positive, and not as negative as frequent blushers might believe—signaling positive traits in an individual.

So, whatever the reason, don't try to hide your blushing. That just makes it worse.

Right-handedness

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We all know more people are right-handed than left-handed. You most certainly learned that in elementary school, when you noticed that only a couple weirdos held their pencils in their left hands. (If you're left-handed and reading this, our apologies—it's not your fault you're a freak.)

Scientists have been studying handedness for over 160 years without figuring out much of anything. It is possible that hand-preference is genetic, but it is definitely non-Mendelian—i.e., there's no way way to predict a kid's handedness by looking at their parents. More plausibly, handedness can be heavily influenced by social and cultural mechanisms, such as in school, with some teachers forbidding the learning of left-handed writing. Some research even suggests left-handedness can be caused by some sort of brain trauma during birth—but we're going to go out on a limb and say that one's a stretch. Whatever the reason, right-handedness is clearly here to stay.

In reality, left-handed people are lucky, and we apologize for the name-calling earlier. We're just jealous, because southpaws naturally have the upper hand in baseball.

Dreaming

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British new wave duo the Eurythmics may claim that "sweet dreams are made of this," and, really, who are we to disagree—especially when we're not really sure what "this" is? You can travel the world and the seven seas and still have no idea why on Earth humans have dreams. There isn't really even a universally accepted definition of what a dream even is. Nonetheless, we're pretty sure we're all on the same page as to what we mean by "dreaming"—so why do we have them?

Darren M. Lipnicki from the Center for Space Medicine Berlin has argued that Earth's geomagnetic field is responsible for the "bizarreness" of our dreams, as geomagnetic activity may be linked to melatonin secretion, and thus linked to dreams—but, unsurprisingly, further research is required to prove this out-of-this-world idea. Sigmund Freud suggested that dreams represent our hidden desires, while another hypothesis claims that dreams may act as a way to simulate threatening situations, letting us react more appropriately if such a situation was to happen in real life, increasing our chances of survival. Some psychologists believe dreams regulate our long-term moods or act as our brain's way of cataloguing daily memories.

Some people even use dreams to implant ideas deep into our consciousness, causing drastic real-world consequences … wait, that might have just been in a movie.

Consciousness

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René Descartes once wrote, "I think, therefore I am." As useful as inarguable as that may be, the French philosopher hasn't really helped us answer the biggest mystery of all: why is human consciousness so advanced that we are capable of creating the Mona Lisa, MySpace and My Chemical Romance? How did we come so far that we can ponder our own existence, and question our role in the seemingly infinite universe, while—at the same time—scroll through dozens, if not hundreds, of pictures of cats playing with boxes?

Human consciousness is truly the greatest mystery there's. It is, in essence, the very mystery of life. And, honestly, science isn't much help. Sure, some scientists have figured out that it's the results of neurons firing in your brain in unique ways, but that's just the mechanism, and it tells us surprisingly little. In November 2016, some clever neurologists at the Beth Israel Deaconess Medical Center also claimed to have "pinpointed the regions of the brain that may play a role maintaining [consciousness]"—surely a shocking discovery, but we forgive you if your mind isn't blown by the revelation that the seat of your consciousness is somewhere in your brain. The Division of Anthropology at the American Museum of Natural History claims that the origin of human consciousness was an accident, while others at Princeton claim that our awareness is "a construct of the social perceptual machinery." Fight the power, man!

The deeper you dig into the leading research on human consciousness, the more you realize we're not really any closer to finding a definitive answer than we were ages ago. Thus, at least for now, we're back to turning to Descartes.